U.S. patent application number 09/837075 was filed with the patent office on 2001-12-06 for steering wheel torque and position sensor.
Invention is credited to Hershberger, Jeffery, Lewis, John T., Mitchell, Steven R., Schlabach, Roderic A., White, James E..
Application Number | 20010048301 09/837075 |
Document ID | / |
Family ID | 46257698 |
Filed Date | 2001-12-06 |
United States Patent
Application |
20010048301 |
Kind Code |
A1 |
Schlabach, Roderic A. ; et
al. |
December 6, 2001 |
Steering wheel torque and position sensor
Abstract
A sensor for measuring torque and position of a shaft having an
internal torsion bar. The sensor has a torque sensor, located in
the housing and connected to the shaft. The torque sensor has a
rotor in electrical contact with a first and second resistive track
disposed on an opposed disc. A position sensor is located in the
housing and is connected to the shaft. The position sensor has a
third contactor mounted to the housing in electrical contact with a
third resistive track located on the disc. Several electrical
terminals are located in the housing and are electrically
communicated with the contactors to provide an electrical signal
indicative of the torque and position of the shaft to an external
electrical circuit. A slip ring is attached between the rotor and
the housing. The slip ring has a fourth and fifth contactor in
contact with the torque sensor. The slip ring is adapted to
electrically connect the torque sensor to the electrical
terminals.
Inventors: |
Schlabach, Roderic A.;
(Goshen, IN) ; Hershberger, Jeffery; (Elkhart,
IN) ; Lewis, John T.; (Granger, IN) ;
Mitchell, Steven R.; (Niles, MI) ; White, James
E.; (Warsaw, IN) |
Correspondence
Address: |
Mark P. Bourgeois
CTS Corporation
905 West Boulevard North
Elkhart
IN
46514
US
|
Family ID: |
46257698 |
Appl. No.: |
09/837075 |
Filed: |
April 18, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
09837075 |
Apr 18, 2001 |
|
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|
09564313 |
May 3, 2000 |
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Current U.S.
Class: |
324/207.2 ;
324/207.25 |
Current CPC
Class: |
G01L 5/221 20130101;
B62D 15/0215 20130101; B62D 6/10 20130101; G01L 3/107 20130101 |
Class at
Publication: |
324/207.2 ;
324/207.25 |
International
Class: |
G01B 007/14 |
Claims
What is claimed is:
1. A torque sensor for measuring the torque applied to a first and
second shaft connected by a torsion bar, the sensor, comprising: a)
a housing having apertures at each end thereof, the shafts passing
through the housing; b) a rotor, located in the housing and
connected to the first shaft, the rotor having a top surface, a
bottom surface and a side surface, the rotor further having a first
and second contactor located on the bottom surface and a first and
second conductive track located on the side surface, the conductive
tracks in electrical contact with the first and second contactors;
c) a rotating disc connected to the second shaft, the disc having a
top surface and a bottom surface; d) a first and second resistive
track disposed on the top surface of the disc, the first and second
contactor contacting the resistive tracks; e) a third and fourth
contactor located in the housing and in electrical contact with the
conductive tracks; and f) a first and second electrical terminal
located in the housing and electrically communicated with the third
and fourth contactors for providing an electrical signal indicative
of the torque on the shafts to an external electrical circuit.
2. The sensor according to claim 1, wherein the sensor further
comprises: a) a third resistive track disposed on the bottom
surface of the disc; b) a fifth contactor in contact with the third
resistive track; and c) a third electrical terminal located in the
housing and electrically communicated with the fifth contactor for
providing an electrical signal indicative of the rotary position of
the shafts to an external electrical circuit.
3. The sensor according to claim 1, wherein the sensor further
comprises: (a) a third and fourth conductive track disposed on the
bottom surface of the disc; (b) a sixth and seventh contactor in
contact with the third and fourth conductive tracks; and (c) a
third and fourth electrical terminal located in the housing and
electrically communicated with the sixth and seventh contactor, the
third and fourth terminals connectable to a source of power and
ground for providing the source of power to the sensor.
4. The sensor according to claim 1, wherein a conductor line
electrically connects the first and second resistive tracks.
5. The sensor according to claim 4, wherein a first edge around
electrically connects the conductor line to the third resistive
track.
6. The sensor according to claim 4, wherein a second edge around
electrically connects the conductor line to the third conductive
track.
7. The sensor according to claim 4, wherein a third edge around
electrically connects the conductor line to the fourth conductive
track.
8. The sensor according to claim 1, wherein an upper carrier is
attached to first shaft, the rotor attached to the upper
carrier.
9. The sensor according to claim 8, wherein a concentricity
compensator is mounted between the upper carrier and the rotor.
10. The sensor according to claim 1, wherein a lower carrier is
attached to the second shaft, the disc attached to the lower
carrier.
11. A sensor for measuring torque and position of a shaft having an
internal torsion bar, the sensor, comprising: (a) a housing having
apertures at each end thereof, the shafts passing through the
housing; (b) a torque sensor, located in the housing and connected
to the shaft, the torque sensor having a rotor having a first and
second contactor in electrical contact with a first and second
resistive track disposed on an opposed disc; (c) a position sensor,
located in the housing and connected to the shaft, the position
sensor having a third contactor mounted to the housing in
electrical contact with a third resistive track disposed on the
disc; (d) a plurality of electrical terminals located in the
housing and electrically communicated with the contactors for
providing an electrical signal indicative of the torque and
position of the shaft to an external electrical circuit; and (e) a
slip ring attached between the rotor and the housing, the slip ring
having a fourth and fifth contactor in contact with the torque
sensor, the slip ring adapted to electrically connect the torque
sensor to the electrical terminals.
12. The sensor according to claim 11, wherein the slip ring
includes a first and second conductive track on a side of the
rotor, the fourth and fifth contactors in contact with the first
and second conductive tracks.
13. The sensor according to claim 1, wherein the shaft has a first
shaft and a second shaft connected by the torsion bar, an upper
carrier is attached to first shaft, the rotor attached to the upper
carrier.
14. The sensor according to claim 13, wherein a concentricity
compensator is mounted between the upper carrier and the rotor.
15. The sensor according to claim 13, wherein a lower carrier is
attached to the second shaft, the disc attached to the lower
carrier.
16. The sensor according to claim 12, wherein the fourth and fifth
contactors are mounted to the housing.
Description
CROSS REFERENCE TO RELATED AND CO-PENDING APPLICATIONS
[0001] This application is a continuation in part of U.S. patent
application Ser. No. 09/564,313, filed May 3, 2000 and titled,
"Non-Contacting Sensor for Measuring Relative Displacement between
Two Rotating Shafts".
[0002] The foregoing patent has the same assignee as the instant
application and is herein incorporated by reference in entirety for
related and supportive teachings.
BACKGROUND OF THE INVENTION
[0003] 1. Field of the Invention
[0004] This invention relates to sensors. In particular, there is a
sensor that can measure the relative displacement between two
rotating shafts. The sensor can be used to sense the amount of
torque applied to a steering wheel in a vehicle as well as the
position of the steering wheel.
[0005] 2. Description of the Related Art
[0006] Various devices and methods of dealing with the design of
steering wheel sensors are known.
[0007] Examples of prior art steering wheel sensors are shown in
U.S. Pat. Nos. 5,763,793 and 5,837,908. The devices described in
these patents measure torque applied to a steering wheel.
Unfortunately, these devices are very expensive and difficult to
manufacture because of the large number of rotating contacts needed
to collect the electrical signal and then to bring the electrical
signal off the rotating member to a connector. For example, the
device of the '908 patent requires 16 electrical contacts. Since,
the contacts are made of a precious metal typically high in
palladium, they are very expensive and quickly add cost to the
device.
[0008] The automotive industry has been focusing on electrical
assist power steering for vehicles. The electrical assist power
steering unit is an electrical motor attached to the steering
linkage that operates when assist is required. A large amount of
torque on the steering wheel occurs at low speed operation or
during parking. The electrical assist power steering is generally
not needed during high speed operation such as during highway
driving. The major advantages of electrical assist power steering
are first, that it only operates during the short time of turning
and is inoperative the rest of the time and second that it is
simpler to manufacture. In a hydraulic power steering system, the
power steering pump is always being turned by the engine and
represents an energy drain on the motor all the time even though
steering is only performed during a small percentage of the total
time a car is operated. An electrical assist power steering system
requires sensing of torque applied to the steering wheel. The
torque indicates how much force the operator is exerting to move
the wheel. The output signal from a torque sensor is fed into a
control unit which controls the electrical motor of the assist
unit. When the torque sensed is high, the assist applied to the
steering linkage will be high. When the torque sensed is low, the
assist applied to the steering linkage will be low. Unfortunately,
the current electrical assist power steering units tend to
overshoot or overcompensate once it is activated. The operator will
tend to have to counter compensate a small amount with the wheel
during operation so that the wheel does not turn beyond the desired
turning point. It is desirable to provide an advanced electrical
assist power steering system with better operator ergonomics that
feels the same during operation as the current hydraulic power
steering systems. In order to accomplish this, the control unit
needs precise torque information. With a precise torque sensor, the
control unit can operate in various modes. For example, when the
steering wheel rotation is reversed, the rotational position sensor
can sense the reversal and the electric motor can be reversed
before a large reverse torque is built up on the wheel and felt by
the operator. This faster motor reversal leads to better operator
ergonomics.
[0009] In general, a sensor that measures the relative displacement
between two rotating shafts has useful applications in the areas of
industrial machinery, aerospace, electrical power generation and
transportation.
[0010] There is a current unmet need for precise steering wheel
torque sensor that is readily manufacturable at low cost.
Additionally, there is a current unmet need for a sensor to measure
the relative displacement between two rotating shafts.
SUMMARY OF THE INVENTION
[0011] It is a feature of the invention to provide a steering wheel
sensor that can sense torque applied to the steering wheel of a
vehicle and the rotary position of the steering wheel.
[0012] Yet, another feature of the invention is to provide a torque
sensor for measuring the torque applied to a first and second shaft
connected by a torsion bar. The sensor includes a housing having
apertures at each end thereof. The shafts pass through the housing.
A rotor is located in the housing and connected to the first shaft.
The rotor has a top surface, a bottom surface and a side surface.
The rotor further has a first and second contactor located on the
bottom surface and a first and second conductive track located on
the side surface. The conductive tracks are electrical contact with
the first and second contactors. A rotating disc is connected to
the second shaft. The disc has a top surface and a bottom surface.
A first and second resistive track are disposed on the top surface
of the disc. The first and second contactor contact the resistive
tracks. A third and fourth contactor are located in the housing and
are in electrical contact with the conductive tracks. A first and
second electrical terminal are located in the housing and are
electrically communicated with the third and fourth contactors to
provide an electrical signal indicative of the torque on the shafts
to an external electrical circuit.
[0013] The invention resides not in any one of these features per
se, but rather in the particular combination of all of them herein
disclosed and claimed. Those skilled in the art will appreciate
that the conception, upon which this disclosure is based, may
readily be utilized as a basis for the designing of other
structures, methods and systems for carrying out the several
purposes of the present invention. Further, the abstract is neither
intended to define the invention of the application, which is
measured by the claims, neither is it intended to be limiting as to
the scope of the invention in any way.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1 is an exploded perspective view of the preferred
embodiment of a steering wheel torque and position sensor.
[0015] FIG. 2 is a cross sectional view of the sensor of FIG. 1 in
an assembled state.
[0016] FIG. 3 is an enlarged perspective view of the rotor.
[0017] FIG. 4 is a bottom view of the element.
[0018] FIG. 5 is a side view of the element.
[0019] FIG. 6 is top view of the element.
[0020] FIG. 7 is an enlarged perspective view looking into the
housing.
[0021] It is noted that the drawings of the invention are not to
scale. The drawings are merely schematic representations, not
intended to portray specific parameters of the invention. The
drawings are intended to depict only typical embodiments of the
invention, and therefore should not be considered as limiting the
scope of the invention. In the drawings, like numbering represents
like elements between the drawings.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0022] Referring to FIGS. 1 and 2 there is a sensor assembly 10
shown. In particular, sensor assembly 10 has a housing 12. Housing
12 has a bottom 12A and a top 12B. Housing bottom 12A has connector
terminals 16 that provide an electrical connection from the inside
of the housing to an external electrical circuit (not shown) using
a wiring harness (not shown). Housing bottom 12A has an aperture 13
and housing top 12B has an aperture 14. Housing bottom 12A forms a
cavity 15. A pair of shafts 20 and 21 extend through apertures 13
and 14, respectively. Shafts 20 and 21 have splines and/or keyways
(not shown) to mate with respective parts of the sensor assembly
10. In the center of the shaft, typically a conventional torsion
bar 11 is used to connect the shafts together. Internal splines
(not shown) or other fixing methods on shafts 20 and 21 would be
used to connect with the torsion bar. The torsion bar transmits the
load between the two shafts and allows flexing or twisting to allow
relative angular displacement of the shafts in proportion to the
amount of torque placed on the shafts. In an automotive
application, shaft 20 can be a steering wheel shaft that connects
to a steering wheel and shaft 21 can be a steering linkage shaft
that connects to a steering linkage gear box. The amount of
difference in the relative rotational displacement of shaft 20 and
21 is proportional to the magnitude of torque being applied to the
steering wheel. A snap ring 17 retains lower carrier 36 against
shaft 21.
[0023] Sensor assembly 10 has a torque sensor 22 and a position
sensor 24 contained within housing 12. The torque sensor 22
generates an electrical signal proportional to the amount of
angular displacement between shafts 20 and 21. The position sensor
24 generates an electrical signal that corresponds to the
rotational position of the shafts.
[0024] An upper carrier 26 is connected to shaft 20 and a lower
carrier 36 is connected to shaft 21. The upper carrier 26 has a
bore 30 that passes through carrier 26. Four arms 28 extend
radially away from carrier 26. A pair of posts 29 extends
downwardly from two of the arms 28. Several projections 31 extend
into bore 30 and mate with the splines on shaft 20.
[0025] A lower carrier 36 is connected to shaft 21. The lower
carrier 36 has a bore 40. Three arms 38 extend radially away from
carrier 36. Several projections 41 extend into bore 40 and mate
with the splines on shaft 21.
[0026] A concentricity compensator 70 has a concentricity disc 71
with four slots 72. Disc 71 is engaged with upper carrier 26. Two
of the slots 72 fit over and are engaged with posts 29 of upper
carrier 26. The concentricity compensator 70 allows sensor 10 to
rotate and perform properly when the axes of rotation of shafts 20
and 21 are slightly non co-axial.
[0027] Referring further to FIG. 3, a slip ring or rotor 50 is
shown. Slip ring 50 has a bore 51 extending therethrough. Slip ring
50 has a top surface 52, a bottom surface 53, an outer side surface
54 and an inner side surface 55. A pair of pins 56 extend upwardly
from surface 52. Pins 52 fit into two of slots 72. Slip ring 50
would be injection molded out of plastic. A pair of conductive
tracks or circuit lines 58 and 59 are located on outer side surface
54. Tracks 58 and 59 are electrically conductive. A pair of support
blocks 60 are located on surface 53 adjacent inner side surface 55.
A pair of wiper arms or contactors 62 and 63 are mounted to support
block 60. Contactor 62 is fastened to block 60 by heat staking over
pin 64. A pair of metal strips 65 and 66 are insert molded into
ring 50. Metal strip 65 electrically connects contactor 62 to track
59. Metal strip 66 electrically connects contactor 63 to track
58.
[0028] Referring further to FIGS. 4, 5 and 6, a ceramic substrate
80 is shown. Substrate 80 has a bore 81 extending therethrough.
Three notches 88 extend into substrate 80 from bore 81. Substrate
80 has a top surface 82 and a bottom surface 83. Substrate 80 is
preferably formed from conventional alumina ceramic. A pair of
cermet resistors 84 and 85 are formed on surface 82. Resistors 84
and 85 are formed by screening and firing a conventional thick film
cermet resistor material. Resistors 84 and 85 measure the torque on
the shafts. Conductive lines 86 connect resistors 84 and 85 to edge
around 87. Conductive lines 86 and edge around 87 are formed from
conventional thick film conductor material. A circular resistive
track 89 is formed on surface 83. A pair of circular conductive
tracks 90 and 91 are formed on surface 83. Resistive track 89
measures the rotary position of the steering wheel.
[0029] Referring now to FIGS. 1 and 7, terminals 16 are connected
to contactors or wipers 101, 102, 103 and 112. Contactors 101, 102,
103 and 112 are mounted on the bottom of housing 12. Terminals 16
are also connected to contactors 104 and 105. Contactors 104 and
105 are mounted on blocks 108 and 109, respectively.
[0030] Referring to FIG. 2 and the other figures, when sensor 10 is
assembled, contactors 62 and 63 are in contact with resistors 84
and 85. Contactor 101 is in contact with resistive track 89.
Contactor 102 is in contact with conductive track 90. Contactor 103
is in contact with conductive track 91. Contactor 104 is in contact
with conductive track 58. Contactor 102 is in contact with
conductive track 59. Contactor 112 is in contact with resistive
track 89. Contactor 112 is positioned 90 degrees from contactor 101
so that an electrical signal from contactor is 90 degrees out of
phase with an electrical signal from contactor 101.
[0031] Sensor 10 operates as follows: Shaft 20 is engaged with
upper carrier 26 which is connected to rotor 50. Shaft 21 is
engaged with lower carrier 36 which is engaged with substrate 80. A
source of power or voltage of about 5 volts is applied to terminal
16B which is connected to contactor 103 which is in electrical
contact with conductive track 91. A ground is connected to terminal
16C which is connected to contactor 102 which is in electrical
contact with conductive track 90. Track 91 is in electrical
connection with resistors 84, 85 and resistive track 89 through
edge around 87 and supplies electrical power to these
components.
[0032] When shafts 20 and 21 rotate the same or rotate co-axial
with each other, element 80 rotates tracks 89, 90 and 91 about
contactors 101, 102, 103 and 112. Outermost track 89 is in
electrical communication with terminal 16D through contactors101.
Similarly, outermost track 89 is in electrical communication with
terminal 16F through contactor 112. As element 80 rotates,
electrical signals indicating the rotational position of the
steering wheel are generated at terminals 16D and 16F. The voltages
at terminals 16D and 16F will vary from 0 to 5 volts and then back
to 0 again. The signals at terminals 16D and 16F are delayed or
offset by 90 degrees.
[0033] Contactors 62 and 63 are in contact with resistors 84 and
85. When no torque is applied to shafts 20 and 21 as they rotate,
the relative positions of contactors 62 and 63 with respect to
resistors 84 and 85, respectfully are unchanged and the resulting
electrical signal on contactors 62 and 63 are unchanged.
[0034] However, when shafts 20 and 21 do not rotate with the same
rotational displacement, the relative positions of contactors 62
and 63 on element 80 changes. The resulting electrical signals on
contactors 62 and 63 also changes. The more torque that is applied
then the larger the change in electrical signal. Therefore,
resistors 84 and 85 generate an electrical signal that is
proportional to the relative rotational displacement of shafts 20
and 21. The resulting electrical signals from resistors 84 and 85
are of equal and opposite slopes.
[0035] Contactors 62 and 63 are connected to conductive tracks 59
and 58 through metal strips 65 and 66. Wipers 104 and 105 are in
contact with tracks 58 and 59. Wipers 104 and 105 and tracks 58 and
59 provide the connecting mechanism to get the electrical signals
that are proportional to torque off of substrate 80 and onto
terminals 16A and 16E. Wipers 104 and 105 are electrically
connected to terminals 16A and 16E.
[0036] An external electrical circuit (not shown) would be
connected to terminals 16A-16F. The external circuitry can
condition the electrical signals and control other mechanisms. For
example, in an automotive steering wheel application, the two
shafts can be connected to a steering wheel and to a steering
linkage. In this case, the electrical signal is proportional to the
amount of torque placed on the steering wheel and can be useful to
control an electric power assist steering system. A position
electrical signal provides a signal regarding the steering wheel
position.
[0037] One of ordinary skill in the art of designing and using
sensors will realize many advantages from studying and using the
preferred embodiment. For example, the sensor uses few precious
metal contactors. Another advantage is that the disc containing the
resistors rotates. The invention provides a robust cost effective
solution to the problem of sensing steering wheel torque and
position.
[0038] While the invention has been taught with specific reference
to these embodiments, someone skilled in the art will recognize
that changes can be made in form and detail without departing from
the spirit and the scope of the invention. The described
embodiments are to be considered in all respects only as
illustrative and not restrictive. The scope of the invention is,
therefore, indicated by the appended claims rather than by the
description. All changes that come within the meaning and range of
equivalency of the claims are to be embraced within their
scope.
* * * * *